Magnetic memory devices are promising candidates for novel alternative memory devices, in part, because of their non-volatile characteristics such as high-speed write and read operations, high integration density, and data rewritability capacity.
Conventional magnetic memory devices may employ a magnetic tunnel junction pattern (MTJ pattern) as a data storage unit. A digit and a bitline may be disposed under and over an MTJ pattern, respectively. The digit line and the bitline may intersect each other. Electric fields generated from the digit lines and the bitline may be applied to the MTJ pattern to vary the resistance of the MTJ pattern. The amount of current flowing through the MTJ pattern may vary with the variation of the resistance of the MTJ pattern. The variation of the amount of current flowing through the MTJ pattern may be sensed in order to judge whether information stored in a unit cell of a magnetic memory device is logic “1” or “0”.
An MTJ pattern may include two magnetic substances and a tunnel barrier layer interposed therebetween. The resistance of the MTJ pattern may vary with magnetization directions of the magnetic substances. That is, a resistance R1 of the MTJ pattern may be lower than a resistance R2 (“R1” being a resistance of the MTJ pattern when the magnetization directions of the magnetic substances are identical to each other, and “R2” being a resistance of the MTJ pattern when the magnetization directions thereof are different from each other).
A conventional method of forming an MTJ pattern is described with reference to FIG. 1. Specifically referring to FIG. 1, an insulation layer 2 is formed on a semiconductor substrate 1. A bottom magnetic layer, a tunnel barrier layer and a top magnetic layer are sequentially formed on the insulation layer 2. A photoresist pattern 7 is formed on a predetermined area of the top magnetic layer. Using the photoresist pattern 7 as a mask, the top magnetic layer, the tunnel barrier layer and the bottom magnetic layer are successively etched to form a lower magnetic pattern 3, a tunnel barrier pattern 4 and an upper magnetic pattern 5, which are stacked in the order recited. In this instance, the etching process employed is a reactive-ion etching (RIE) process. The lower magnetic pattern 3 includes a magnetic substance whose magnetization direction is pinned, while the upper magnetic pattern 5 includes a magnetic substance whose magnetization direction is variable. The tunnel barrier pattern 4 includes an insulating substance.
During the RIE process, etch residues 8 may be produced at a sidewall of a MTJ pattern. The etch residues may not be easily removed. Since the upper magnetic pattern 5 may conventionally include nickel iron (NixFey) or cobalt ion (CoxFey), the etch residues 8 may contain iron, nickel or cobalt. Thus, the etch residues 8 may contribute to an electrical short circuit with respect to the upper and lower magnetic patterns 3 and 5, respectively. Consequently, intrinsic properties of the MTJ pattern may be altered resulting in a malfunction of the magnetic memory device.
Attempts have been made in an effort to resolve the problems noted above. One such attempt is described with reference to FIG. 2 and FIG. 3.
FIG. 2 and FIG. 3 present cross-sectional views illustrating a modified conventional method of forming an MTJ pattern of a magnetic memory device. Specifically referring to FIG. 2 and FIG. 3, an insulation layer 11 is formed on a semiconductor substrate 10. A bottom magnetic layer 12, a tunnel barrier layer 13, and a top magnetic layer 14 are sequentially formed on the insulation layer 11. A photoresist pattern 15 is formed on a predetermined area of the top magnetic layer 14. Using the photoresist pattern 15 as a mask, the upper magnetic pattern 15 is etched in a direction toward a top surface of the tunnel barrier layer 13 to form an upper magnetic pattern 14a. 
Although not shown in the referenced figures, as understood by one of ordinary skill in the art, after the photoresist pattern 15 is removed, the tunnel barrier layer 13 and the bottom magnetic layer 12 are successively patterned to form a lower magnetic pattern and a tunnel barrier pattern, which are stacked in the order recited. Due to, at least in part, the photoresist pattern being formed using the patterning process, the upper magnetic pattern 14a may be protected.
According to the modified method, the upper magnetic pattern 14a is formed using the tunnel barrier layer 13 as an etch-stop layer. When the lower magnetic pattern is formed, the upper magnetic pattern 14a may be protected to prevent a short between the lower magnetic pattern and the upper magnetic pattern 14a. 
Etching the top magnetic layer 14 may be accomplished by employing an RIE process. In the some instances, the thickness of the tunnel barrier layer 13 may be unsuitable for its use as an etch-stop layer. More specifically, the tunnel barrier layer 13 may suffer from plasma damage and/or physical damage, at least in part, because of the RIE process. Thus, the lower magnetic pattern and the upper magnetic pattern 14a may be shorted and it may be less likely to achieve reproducibility of the RIE process. In an attempt to overcome the disadvantages described above, the top magnetic layer 14 may be etched using a wet etch.
An etchant solution including dicarboxylic acid is described in U.S. Pat. No. 6,426,012 to O'Sullivan et al. (hereinafter, “O'Sullivan”). According to O'Sullivan, a top magnetic film layer including nickel iron (NixFey) or cobalt iron (CoxFey) is etched using a wet etch process employing the etchant solution including dicarboxylic acid. The dicarboxylic acid is, for example, glutaric acid, adipic acid or suberic acid. However, the described etchant solution may not be capable of etching the nickel iron (NixFey) or cobalt iron (CoxFey) to the extent desired for the manufacturing processes described herein.